The invention relates to use of a hydraulic accumulator as a means of storing energy to assist in meeting intermittent load-acceleration demands in a hydraulic drive of the load.
The text Industrial Hydraulics, Pippinger/Hicks, McGraw-Hill, Second Ed., at Section 6.8 ("Fluid Storage Accumulators"), pages 189/190, shows and describes a conventional use of a hydraulic accumulator as a volume-storage unit. Fluid from a fixed-delivery pump passes through a first check valve as long as work-load pressures are less than a relief-valve setting. When work-load pressures rise, e.g., to within 20 percent of the relief-valve setting, fluid can pass through a sequence valve to the accumulator, until the accumulator is fully charged, whereupon the relief valve will assure against further pressure rise. A variable-delivery pump is described as an alternative to the fixed delivery pump. In either case, the accumulator-stored volume and pressure are available to assist the pump output in response to a range of varying load demand.
Berkman, et al. U.S. Pat. No. 3,238,722 describes a more complex system of using a hydraulic accumulator for delivering stored pressure fluid for transient acceleration of a load, which happens to involve slewing angular acceleration of a crane about a vertical axis; the system also incorporates means for utilizing angular slewing momentum to restore hydraulic fluid to the accumulator during the deceleration phase of slewing. The system requires a high-pressure circuit with a first accumulator and a low-pressure circuit with a second accumulator, plus relatively elaborate control interconnections between components of these circuits.